ITBO990197A1 - SELF ADAPTIVE METHOD OF CHECKING THE TITLE IN AN INJECTION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE. - Google Patents

Description

DESCRIPTION

of the patent for industrial invention

The present invention relates to a self-adaptive method of controlling the title in an injection system for an internal combustion engine.

As is known, most of the vehicles currently on the market have injection systems equipped with count control systems with the purpose of regulating the quantity of fuel to be delivered to each individual cylinder in order to obtain a title to the exhaust as close as possible. possible to an objective title.

Some of these control systems are self-adaptive, i.e. they are able to recover the production losses that cause the engine and the exhaust system to deviate from the nominal case foreseen during the calibration phase and to compensate in part also the variations due to the '' aging of the engine and exhaust system components, in particular the oxygen sensors and the catalyst.

For example, control systems are known comprising a first and a second oxygen sensor arranged upstream and respectively downstream of the catalyst. The information provided by the sensor located upstream of the catalyst is used to calculate a correction coefficient for a theoretical quantity of fuel to be injected into each cylinder so that the quantity exiting the combustion chamber, upstream of the catalyst, is equal to an objective titer while the information provided by the sensor located downstream of the catalyst is used to apply further corrections to the control parameters calculated on the basis of the information provided by the sensor upstream of the catalyst. In particular, based on the information of the sensor located downstream of the catalyst, an additive coefficient can be calculated which modifies the value of the objective titer.

However, the known solutions have a drawback due to the intrinsic slowness of adaptation and do not allow to obtain information on the functionality of the injection control system, in particular on the oxygen sensors, which can only be obtained with the use of further sensors.

The object of the present invention is to provide a method which is free from the drawbacks described and, in particular, allows a high speed of adaptation.

According to the present invention, therefore, a self-adaptive titre control method is provided for an internal combustion engine (2) provided with a polluting emissions abatement system (4) and with first and second stoichiometric composition sensor means (5) arranged upstream and downstream respectively of said polluting emissions abatement system (4) and capable of generating an upstream composition signal (V1) and, respectively, a downstream composition signal (V2); said method including the steps of:

- determining a correction coefficient (K02) as a function of said upstream composition signal (V1), of said downstream composition signal (V2) and of an objective signal (V °) indicative of an objective exhaust titre;

a) determining an operating quantity of fuel (QF) to be injected into each cylinder of said engine (2) as a function of said correction coefficient (K02);

characterized by the fact that it also includes the phases of:

b) storing a plurality of current values (VAC (i, j)) of an adaptive signal (VA) associated, each, with a respective combination of values of the number of revolutions (RPM) and of the load (L) of said motor ( 2);

c) updating said current values (VAC (i, j)) as a function of said downstream dialing signal (V2);

d) at each engine cycle selecting a said current value (VAC (i, j)) corresponding to the number of revolutions (RPM) and the load (L) of said engine (2) in said engine cycle;

e) generating said adaptive signal (VA) as a function of said current value (VAC (i, j)) selected;

and by the fact that said phase a) includes the phase of:

al) determining said correction coefficient (K02) also as a function of said adaptive signal (VA).

For a better understanding of the present invention, a preferred embodiment thereof is described below, purely by way of non-limiting example and with reference to the attached drawings, in which:

Figure 1 schematically illustrates a title control system according to the present invention;

Figures 2 to 5 illustrate flow diagrams relating to the control method according to the present invention;

- Figures 6a to 6c illustrate examples of temporal trends of signals used in the method according to the present invention.

In Figure 1, 1 indicates, as a whole, a system for controlling the title for an internal combustion engine 2 connected, through an exhaust manifold 3, to a system for reducing polluting emissions 4, typically comprising a pre-catalyst and a catalyst.

Upstream and downstream of the polluting emissions abatement system 4 there are a first stoichiometric composition sensor of the exhaust gases, hereinafter referred to as the upstream probe 5, and, respectively, a second stoichiometric composition sensor of the exhaust gases , hereinafter referred to as the downstream probe 6.

The probes 5 and 6, which, conveniently, can be of the linear LAMBDA type, generate respective composition signals upstream V1 and downstream V2 representative of the stoichiometric composition of the exhaust gases at the inlet and, respectively, at the outlet of the system. of abatement of polluting emissions 4.

The control system 1 further comprises a control unit 10 which receives the composition signals V1 and V2 at the input and a plurality of engine parameters and provides at the output, at each engine cycle, an actuation signal QF representative of the quantity of fuel to be injected into each cylinder .

In particular, the control unit 10 comprises a downstream control block 17 receiving in input the downstream composition signal V2 and providing at the output, at each engine cycle, a correction signal Vc; a filtering block 20 of the low-pass type receiving in input the downstream composition signal V2 and providing at its output a filtered correction signal VCF; and an adaptive parameter management block 18, receiving in input the downstream composition signal V2, the correction signal Vc, the filtered correction signal VCF, the number of revolutions RPM and the load L of the motor 2 and providing an output VA adaptive signal.

The control unit 10 further comprises a first adder block 13 receiving in input the upstream composition signal V1 and the adaptive signal VA and providing in output a first sum signal VSi equal to the sum of the upstream composition signal Vi and the adaptive signal VA; a second summing block 14 receiving in input the correction signal Vc and an objective signal V ° representative of an objective titer λ ° and providing at its output a second sum signal VS2 equal to the sum of the correction signal Vc and the objective signal V °; an upstream control block 12 receiving in input the first and second sum signals VS1, VS2 and providing at the output, at each motor cycle and in a known way and therefore not described in detail, a correction coefficient K02; and a fuel actuation block 15 receiving at the input the correction coefficient K02 and a plurality of engine parameters, for example the number of revolutions RPM and the load L of the engine 2 and supplying at the output, in a known way and therefore not described in detail , the QF actuation signal.

The adaptive parameter management block 18 comprises a memory 21 containing a map M and an update block 22 of the map M operating according to an adaptation strategy described in detail below.

In particular, the update block 22 receives in input the downstream composition signal V2, the correction signal Vc, the filtered correction signal VCF and the number of revolutions RPM and the load L of the motor 2 and outputs a counter of adaptations performed NA and updated values VAN (i, j) used to update the map M stored in memory 21 in the manner described in detail below.

The memory 21 receives in input the number of revolutions RPM and the load L of the motor 2 as well as the updated values VAN (i, j) and in the map M for each combination of the values of the number of revolutions RPM and of the load L a respective current value VAc (i, j) - At each motor cycle, based on the values assumed by the number of revolutions RPM and the load L, a current value VAc (i, j) is selected and supplied as the output of memory 21 and defines the adaptive signal VA provided by adaptive parameter management block 18 in the current motor cycle.

Finally, the control unit 10 comprises a diagnosis block 25 receiving in input the counter of adjustments carried out NA and the updated values and supplying a plurality of signals at the output to a system supervisor, not shown.

In particular, as described in more detail below, the diagnosis block 25 implements a diagnosis algorithm based on the verification of the congruence of the composition signals V1 and V2, coming from the probes 5 and 6, and able to generate, consequently, a signal of correct operation of the title 1 control system or an error signal.

As previously mentioned, the map update block 22 implements an adaptation strategy for updating the map M. This strategy, which will be described below with reference to Figures 2 to 5, is performed at each engine cycle and is based on on the trend of the downstream composition signal V2 and of the correction signal Vc. In particular, it is verified whether the downstream composition signal V2 and the correction signal Vc remain within a dead band BM, defined around a downstream target value V2 °, and, respectively, within a safety band BS, defined around an objective correction value Vc °, as illustrated in Figures 6a and 6c, respectively.

With reference to Figure 2, some preliminary tests are initially carried out in sequence to carry out the update procedure. In detail, it occurs if the map update function M has been enabled during calibration (block 100), if the downstream control block 17 is active (block 110) and if the engine state has remained unchanged with respect to the engine cycle previous (block 120). In all three cases, if the check has a negative result, the updating procedure is abandoned (block 130), while in the event of a positive result the next test is performed.

In particular, the test on the downstream control block 17 (block 110) is performed because this block can be temporarily deactivated, for example in the event of a fault or in particular operating conditions of the motor 2, while the motor status test is performed because the update of the map M can only be carried out in conditions of steady state RPM and load L.

In fact, the presence of the polluting emissions abatement system 4 entails a delay of a few tens of seconds between the variations in the compositions of the exhaust gases upstream and downstream of the abatement system 4 itself and it is therefore necessary to let a transient run out. .

In case of positive result of the test on the motor status (block 120), a test is carried out on the permanence of the downstream composition signal V2 inside the dead band BM (block 140). The test consists in verifying whether the downstream composition signal V2 is currently within the dead band BM and, subsequently, whether at least one of the following two conditions exists:

- the downstream composition signal V2 has remained inside the dead band BM without interruption for a dead band time TBM greater than a threshold dead band time TBMS; And

- the number of NT transitions that the downstream composition signal V2 has carried out across the downstream target value V2 °, without exiting the dead band BM, is greater than a number of threshold transitions NTS.

If the stay test in dead band (block 140) described above is successful, an adaptation procedure in dead band BM (block 150) is carried out, while otherwise an adaptation procedure out of dead band BM (block 160) is performed. ).

Figure 3 illustrates the block diagram relating to the deadband adaptation procedure BM (block 150).

According to what is illustrated in this figure, a test is initially carried out on the correction signal Vc (block 151). Since the correction signal Vc represents the action performed by the downstream control block 17 to keep the downstream composition signal V2 close to the downstream target value V2 °, the test on the correction signal Vc aims to verify whether, based on the extent of this action, it is actually appropriate to update the M map.

In particular, defined a safety band time TBS as the sum of the intervals T1, T2, ..., contained in the dead band time TBM, during which the correction signal Vc remains within the safety band BS ( as shown in Figure 6b), it is checked if the ratio between the safety band time TBs and the dead band time TBM exceeds a first predetermined threshold X2 between 0 and 1.

If the test is successful, the update of the map M is not considered necessary and the update procedure in dead band BM is abandoned (block 158). Otherwise, an updated value VAN (i, j) corresponding to the current load conditions L and RPM number of motor 2 is calculated and stored in memory 21 in place of the corresponding current value VAC (i, j) {block 152).

The calculation of the updated value VAN (i, j) is carried out by adding the present value of the filtered correction signal VCF to the current value VAC (i, j), i.e .:

All other current values VAC (i, j), corresponding to different load conditions L and RPM number of motor 2, are left unchanged.

Subsequently, an adaptation flag FA is set to the logical value "TRUE" (block 153) to indicate that the adaptation procedure in deadband BM has been performed, the deadband time TBM and the number of transitions NT are reset {block 154) and the counter of adjustments performed NA is increased by one unit (block 155).

The number indicated by the counter of adaptations carried out NA refers to the last engine start-up period, indicative of the time elapsed since the last engine start-up 2.

Finally, the count of a downstream control time Tv (block 156) indicative of the time elapsed since the last activation of the downstream control block 17 is stopped, and the adaptation procedure in dead band BM is terminated (block 158).

Figure 4 illustrates the block diagram relating to the out-of-dead band adaptation procedure BM (block 160).

As illustrated in this figure, a test is initially carried out to verify whether a deadband adaptation procedure has already been performed (block 161). In the event of a positive outcome, the BM out-of-dead band adaptation procedure is abandoned (block 167). In the event of a negative result, a further test is carried out on a total dead band time TBMT (block 162), which is equal to the sum of the dead band times TBM included in the downstream control time Tv (Figure 6c).

In particular, it occurs if the ratio between the dead band TBM time and the downstream control time Tv exceeds a second predetermined threshold X2 between 0 and 1. If successful, the out-of-dead band BM update procedure is abandoned (block 167), otherwise the updated NPV values (i, j) (block 163) are calculated.

In practice, the update of the map M is carried out when the action of the downstream control block 17 is not sufficient to guarantee the permanence of the downstream composition signal V2 within the dead band BM for a minimum time, starting from the insertion of the downstream control block 17 itself. In fact, it is believed that the situation described is critical.

The calculation of the updated NPV values (i, j) is carried out according to the following formula:

in which KA is a correction coefficient between 0 and 1. This coefficient is introduced in order to mitigate the extent of the update, since the out-of-dead band adaptation procedure is used in conditions considered to be critical, as noted above. Furthermore, the update concerns all the values of the map M and not only the one corresponding to the current conditions of number of revolutions RPM and load L of engine 2.

Subsequently, the adaptation flag FA is set to the logical value "FALSE" (block 164) to indicate that the out-of-band adaptation procedure BM has been performed and the counter of adaptations performed NA is incremented by one unit (block 165) , ending the BM deadband out-of-band update procedure (167).

Figure 5 illustrates the flow diagram relating to the diagnosis algorithm implemented by the diagnosis block 25.

As illustrated in this figure, it is initially checked whether the diagnosis function has been enabled during calibration (block 200). In the event of a negative outcome, the diagnosis algorithm is terminated (block 300), otherwise it is checked whether a certain number of updates of the map M have already been carried out (block 210).

In particular, if the NA update counter is lower than a predetermined NAS threshold value, the diagnosis algorithm is terminated (block 300), while otherwise a test is performed on the absolute value of the updated VAN values (i, j ) (block 220) verifying if, for at least a combination of values of the number of revolutions RPM and of the load L of the motor 2, the corresponding updated value VAN (i, j) exceeds, in absolute value, a predetermined threshold value of VAS adaptation. This, in practice, is equivalent to believing that the storage in the map M of a too high value is a symptom of non-congruence between the signals detected by the upstream probe 5 and the downstream probe 6 and that, therefore, a situation of irregular operation.

If the condition is true for at least one updated value VAN (i, j), an error counter CE (block 230) is incremented, while otherwise a positive test counter CT performed (block 240) is incremented.

Subsequently, a test is carried out on the counter of positive tests performed CT (block 250). In particular, if this counter exceeds a predetermined threshold number of CTS test counts, the system supervisor is notified that the diagnosis algorithm has been correctly executed (block 260) and the diagnosis algorithm is terminated, otherwise a test is carried out on the error counter CE (block 270).

If the error counter CE has exceeded a threshold number of error counts CES an error message is sent to the system supervisor, for example by setting an error flag FE to the logical value "TRUE", and the diagnostic block 25 is disabled (block 280), while otherwise the diagnosis algorithm is terminated.

In block 280, a status flag Fs is also placed at a logic value corresponding to an error signaling, so that, at the subsequent start-up of the engine 2, a stored value Δ is used to modify the values of the map M which they exceed the VAS adaptation threshold value. · In particular, the Δ value is added to the quoted values, if they have a negative sign; if, on the other hand, the sign is positive, the value Δ is subtracted. In this way, when the motor 2 is restarted, the values of the map M which gave rise to the error signal are brought back to less critical values; consequently, if the causes of the error are temporary and are removed by switching off the engine 2, a condition of correct operation is restored when the engine is restarted.

If, on the other hand, the causes of the error persist, a new fault signal will necessarily be sent.

The method described has the following advantages. In the first place, by updating the VAC coefficients (i, j) of the M map it allows to compensate both the production losses and the deviations from the nominal performances due to the aging of the parts that make up the system.

Furthermore, the method is able to quickly calculate these coefficients; in fact, the choice of these coefficients is made, at each engine cycle, exclusively on the basis of the current conditions of number of revolutions RPM and load L.

A further advantage is constituted by the fact that the method allows to carry out in a simple way a diagnosis on the congruence of the information coming from the stoichiometric composition sensors without the need to use sensors of another type.

The diagnosis algorithm is also fast; in fact, the element that has a predominant influence on the time necessary for the calculation of the NPV coefficients (i, j) is the system for abatement of polluting emissions 4, which, as already mentioned, causes a delay of a few tens of seconds between variations of the upstream composition signal Vi and the corresponding variations of the downstream composition signal V2.

Therefore, the only condition required to be able to carry out the diagnosis is that the operating conditions of the engine 2 remain stationary for a sufficient time, determined by the polluting emissions abatement system 4.

Finally, it is clear that modifications and variations may be made to the described method which do not depart from the scope of protection of the present invention.

Claims (18)

R I V E N D I C A Z I O N I 1. Self-adaptive titre control method for an internal combustion engine (2) equipped with a polluting emissions abatement system (4) and with first and second stoichiometric composition sensor means (5, 6) arranged upstream and, respectively, at downstream of said polluting emissions abatement system (4) and able to generate an upstream composition signal (V1) and, respectively, a downstream composition signal (V2); said method including the steps of: al) determining a correction coefficient (K02) as a function of said upstream composition signal (V1), of said downstream composition signal (V2) and of an objective signal (V °) indicative of an objective exhaust titre; a2) determining an operating quantity of fuel (QF) to be injected into each cylinder of said engine (2) as a function of said correction coefficient (K02); characterized by the fact that it also includes the phases of: b) storing a plurality of current values (VAC (i, j)) of an adaptive signal (VA) associated, each, with a respective combination of values of the number of revolutions (RPM) and of the load (L) of said motor ( 2); c) updating said current values (VAC (i, j)) as a function of said downstream dialing signal (V2); d) at each engine cycle selecting a said current value (VAC (i, j)) corresponding to the number of revolutions (RPM) and the load (L) of the said engine (2) in the said engine cycle; e) generating said adaptive signal (VA) as a function of said current value (VAC (i, j)) selected; and by the fact that said phase a) includes the phase of: all) determining said correction coefficient (K02) also as a function of said adaptive signal (VA). 2. Method according to claim 1, characterized in that said phase all) comprises the step of adding said adaptive signal (VA) to said upstream composition signal (V1). 3. Method according to claim 1 or 2, characterized in that said step c) is preceded by the steps of: f) verifying conditions of permanence of said downstream composition signal (V2) in a dead band (BM) (140); g) carrying out a dead band update procedure (150) if the permanence of said downstream dialing signal (V2) in said dead band (BM) is verified; And h) carrying out an out-of-dead band update procedure (160) if the permanence of said downstream dialing signal (V2) in said dead band (BM) is not verified. 4. Method according to claim 3, characterized in that said dead band (BM) consists of an interval of values assumed by said downstream composition signal (V2) comprising an objective downstream composition value (V2 °). 5. Method according to claim 3 or 4, characterized in that said step f) comprises the steps of: fi) determining a dead band time (TBM) indicative of the time in which said downstream dialing signal (V2) has remained in said dead band (BM); f2) determining a number of transitions in dead band (NT) indicative of the transitions effected by said downstream dialing signal (V2) in said dead band (BM); f3) checking if said dead band time (TBM) is greater than a threshold dead band time (TBMS); And f4) check if said number of transitions in dead band (NT) is greater than a number of transitions in threshold dead band (NTS). 6. Method according to claim 5, characterized in that said step g) comprises the steps of: gl) generating a correction signal (Vc) as a function of said downstream composition signal (V2); g2) verifying conditions of permanence of said correction signal (Vc) within a safety band (BS) (151); And g3) if the permanence of said correction signal (Vc) within said safety band (BS) is not verified, calculate one of said updated values VAN (i, j) as a function of said correction signal (Vc) . 7. Method according to claim 6, characterized in that said step g3) comprises the step of calculating one of said updated values VAN (i, j) according to the formula: wherein VAN (i, j) is said updated value, VAC (i, j) is a corresponding said corrected value and VCF is a filtered correction signal obtained by filtering said correction signal Vc. 8. Method according to claim 6 or 7, characterized in that said safety band (BS) is constituted by an interval of values assumed by said correction signal (Vc) comprising an objective correction value (Vc °) - Method according to any one of claims 6 to 8, characterized in that said step g2) comprises the step of: g21) determining a safety band time (TBS) correlated to the sum of the time intervals contained in said dead band time (TBM) during which said correction signal (Vc) remains within said safety band (BS); and g22) checking whether the ratio between said safety band time (TBS) and said dead band time (TBM) is greater than a first predetermined threshold (X1). Method according to any one of claims 5 to 9, characterized in that said step h) comprises the steps of: h1) verifying conditions of permanence of said downstream composition signal (V2) outside said dead band (BM) (162); h.2) if the permanence of said downstream composition signal (V2) outside said dead band (BM) is verified, calculate all said updated values VAN (i, j)) as a function of said correction signal . 11. Method according to claim 10, characterized in that said step h2) comprises the step of calculating all said updated values VAN (i, j)) according to the following formula: wherein VAN (i, j) are said updated values, VCF is a filtered correction signal obtained by filtering said correction signal Vc and KA is a correction coefficient. 12. Method according to claim 11, characterized in that said correction coefficient (KA) is comprised between 0 and 1. 13. Method according to any one of claims 10 to 12, characterized in that said step hi) comprises the steps of: h11) determining a downstream control time (Tv) indicative of the time elapsed since the activation of a downstream control block (17); And hl2) checking whether the ratio between said dead band time (TBM) and said downstream control time (Tv) is greater than a second predetermined threshold (X2). 14. Method according to any one of the preceding claims, characterized in that it further comprises the step of: i) carry out a diagnosis procedure to verify the correct operation of said first and second stoichiometric composition sensor means (5, 6) and of said polluting emissions abatement system (4), based on said updated VAN values (i, j). 15. Method according to claim 14, characterized in that said step i) comprises the step of: 11) comparing absolute values of said updated VAN values (i, j) with at least one adaptation threshold value (VAS) (220). 12) incrementing an error counter (CE) (230) if at least one of the absolute values of said updated VAN values (i, j) is greater than said adaptation threshold value (VAS); And 13) incrementing a counter of positive tests performed (CT) (240) if all the absolute values of said updated values (VAN (i,)) are less than said adaptation threshold value (VAS). 16. Method according to claim 15, characterized in that said step i) further comprises the steps of: 14) comparing said counter of positive tests performed (CT) with a predetermined threshold number of test counts (CTS); And 15) signaling a correct execution of the diagnosis procedure (260) if said positive tests performed (CT) counter is greater than said test count threshold number (CTs); and i6) carrying out an error detection sequence (270, 280, 290) if said counter of positive tests performed (CT) is less than said threshold number of test counts (CTS). Method according to claim 16, characterized in that said error detection sequence step (270, 280, 290) comprises the steps of: 161) comparing said error counter (CE) with a predetermined error count threshold number (CES); 162) generate an error signal (FE) and disable said diagnosis procedure, if said error counter (CE) is greater than said predetermined threshold number of error counts (CEs). 18. Self-adaptive method of title control in an injection system for an internal combustion engine, substantially as described and illustrated with reference to the attached drawings.